This invention relates to the operation of marine motor vessels, and more particularly to a system for determining and displaying the real-time apparent slip for a vessel propeller, as well as recording the same information for analysis at a later time.
Theoretical propeller advance in a non-yielding fluid is equal to the propeller's pitch multiplied by the number of rotations of the propeller. Apparent slip is the percentage of theoretical propeller advance lost in a yielding fluid, such as water. While apparent slip is not a direct measure of propeller efficiency, there is a strong correspondence between the two quantities. All other things being equal, as apparent slip is reduced, vessel speed increases.
Traditional systems for monitoring motor vessel performance focus on the fuel efficiency of the motor vessel engine. None of these traditional systems provide an accurate measurement of apparent slip.
In recreational marine motor vessels (e.g., fishing boats and water ski boats), apparent slip is an important factor in overall vessel performance. Commercial vessels, such as commercial marine transport ships and fishing ships are also affected by apparent slip. A marine motor vessel plays a necessary role in some professions, and the apparent slip of the vessel's propeller directly impacts success in those professions.
For example, in sports fishing, most tournaments are structured such that all teams are allotted the same amount of time on a body of water. It is in a fishing team's interest to have a fishing boat equipped with a propeller that is operating with optimal apparent slip. The team that can move from location to location on the water the fastest, and therefore spend the greatest portion of their allotted time fishing, has the best odds of catching a greater number of large fish and winning the tournament.
Therefore it is desirable to provide a system that measures and records data relating to propeller apparent slip, and that allows comparison of apparent slip for different propellers and under different conditions.